基于功率分配的最优中继选择方案的研究

发布时间：2018-05-19 17:08

本文选题：中继选择 + 功率分配　；参考：《新疆大学》2017年硕士论文

【摘要】：在实际通信系统中,由于山川河流、高楼大厦、雨雪气流等多种因素的影响,在通信链路的传输过程中会有快衰落、慢衰落以及多径衰落现象,通过使用中继转发技术能够降低无线通信传输的中断率、提高通信系统的吞吐量、降低功率消耗并改善边远地区的覆盖范围。在中继协作的无线通信网络中,最值得关注的是各个节点的功率分配、中继节点的选择。功率分配的研究对于现今的中继通信系统十分重要,在含有中继的无线网络系统中,传统模式端到端的通信方式己经没有了,被一个较复杂的两跳通信方式取而代之。功率分配的关键是要研究源节点和中继节点处的发送功率,在这样的无线通信系统中,已被选中的中继节点的各种性能都将直接影响到信道链路的整体质量。本文首先研究了基于功率分配的单路中继选择方案,考虑了一种低自干扰、较高通信质量的无线中继选择方案,源节点和中继节点的功率用拉格朗日极值法来合理分配,目标是使无线通信系统的中断率最小。由各个链路的平均信噪比、发送功率的倒数以及约束条件组成拉格朗日函数,对所组成的拉格朗日函数求极值,得出能使联合函数为最大的功率分配值,把求出的信道参数和功率值代入待发送信息的系数中,对系数和从小到大排序从而选择出最理想的中继节点,结合放大转发方式完成通信。此方案可以在选择较好无线通信链路的同时,又能节约终端能源,降低信号间的干扰。然后针对两路中继选择的最小误码率、信道速率和计算复杂度,提出了带有功率分配、自干扰控制的两路中继选择方案。考虑了最优和次优功率分配算法,最优算法采用二等分法来找出非凸目标函数最优值,次优算法用高信干噪比近似值来描述最优问题;基于功率分配算法提出了两路中继选择的最优标准和次优标准。对以放大转发方式通信的两路中继选择方案,考虑四种优化变量:在连续时隙中每条链路的两个源节点的发送功率、两个中继节点的发送功率。最后的结果表明,两路中继选择的误码率比单路中继选择小,次优选择标准的误码率与最优选择标准几乎相等,计算复杂度低于最优方案的计算复杂度,在实际应用中,可用次优选择方案降低计算复杂度并达到与最优选择方案一样的性能,功率分配及低自干扰的中继选择的研究对于频谱资源有限的无线通信系统是非常有现实意义的。
[Abstract]:In the actual communication system, due to the influence of many factors, such as mountains, rivers, tall buildings, rain and snow, there will be fast fading, slow fading and multipath fading in the transmission process of communication link. By using relay forwarding technology, the outage rate of wireless communication transmission can be reduced, the throughput of communication system can be improved, the power consumption can be reduced and the coverage of remote areas can be improved. In the relay cooperative wireless communication network, the most important issues are the power allocation of each node and the selection of relay nodes. The research of power allocation is very important to the current relay communication system. In the wireless network system with relay, the traditional mode of end-to-end communication is gone, which is replaced by a more complex two-hop communication mode. The key of power allocation is to study the transmission power of the source node and the relay node. In such a wireless communication system, the performance of the selected relay node will directly affect the overall quality of the channel link. In this paper, the single relay selection scheme based on power allocation is studied, and a wireless relay selection scheme with low self-interference and high communication quality is considered. The power of source node and relay node is reasonably allocated by Lagrange extreme value method. The goal is to minimize the interruption rate of the wireless communication system. The Lagrange function is composed of the average signal-to-noise ratio (SNR) of each link, the reciprocal of transmission power and the constraint conditions. The maximum power distribution value of the joint function can be obtained by calculating the maximum value of the Lagrange function. The calculated channel parameters and power values are substituted into the coefficients of the information to be transmitted, the coefficients and the order from small to large are sorted to select the most ideal relay nodes, and the communication is completed by means of amplification and forwarding. This scheme can not only select better wireless communication links, but also save terminal energy and reduce inter-signal interference. Based on the minimum bit error rate, channel rate and computational complexity of two-channel relay selection, a two-channel relay selection scheme with power allocation and self-interference control is proposed. The optimal and sub-optimal power allocation algorithms are considered. The optimal algorithm uses the bisection method to find the optimal value of the non-convex objective function, and the sub-optimal algorithm uses the approximate value of the high signal-to-noise ratio to describe the optimal problem. Based on the power allocation algorithm, the optimal criteria and suboptimal criteria for two-channel relay selection are proposed. Four optimization variables are considered for the two-channel relay selection scheme in the mode of amplification and forwarding: the transmission power of two source nodes in each link in a continuous time slot and the transmission power of two relay nodes. The results show that the BER of the two-channel relay selection is smaller than that of the single-channel relay selection, the BER of the sub-optimal selection standard is almost equal to the optimal selection criterion, and the computational complexity is lower than that of the optimal scheme. The available suboptimal selection scheme reduces the computational complexity and achieves the same performance as the optimal selection scheme. The research of power allocation and low self-interference relay selection is of great practical significance for wireless communication systems with limited spectrum resources.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

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